Field of the Invention
The present disclosure relates to medical devices and methods of using the same. More particularly, the disclosure relates to systems, methods, and apparatus used to diagnose and treat conditions of the eye such as meibomian gland dysfunction and blepharitis, typically involving eyelids, meibomian glands, ducts, orifices, and surrounding tissue.
Description of the Related Art
Meibomian gland dysfunction (MGD) is thought to be the most common cause of evaporative dry eye disease, with studies showing a prevalence ranging from 20% to 60% in the general population. MGD is associated with a failure of meibomian glands to produce an adequate quantity of normal secretions (called meibum). Meibum is a lipid-rich essential component of a healthy tear film. When sufficient meibum is not present in the tear film, the film readily evaporates, leading to evaporative dry eye disease. In some patients, the viscosity and melting point of the meibum may elevate, resulting in thickened meibum that does not flow easily out of the glands. Further, the channel or duct within the meibomian gland may become hyperkeratinized, leading to excessive cellular debris and contributing to the clogging of the gland over time. Once the glands become chronically clogged (inspissated), they may atrophy, and no longer be able to produce or secrete meibum.
Blepharitis is a common chronic inflammatory condition involving the eyelid and eyelid margin, and is often associated with MGD. Studies show a prevalence of blepharitis in the general population ranging from 12% to 47%, with higher prevalence amongst older individuals. In addition to certain causative factors relating to MGD, blepharitis may be caused in part by an abundance of certain bacteria in and around the eye and eyelid. By-products of the bacteria are thought to be irritating to the eye, leading to further inflammation and discomfort to the patient. In addition, several types of common mites may play a role in adding to the inflammation of the meibomian glands or sebaceous glands in and around the eyes. The inflammation caused by these factors can lead to further constriction of the meibomian gland ducts, limiting the flow of meibum from the glands and aggravating the condition.
Diagnosis of meibomian gland dysfunction can be done in many ways. Typical approaches include measurement of tear break-up time (TBUT), staining of various ocular surfaces, and examination of the meibomian glands and their secretions. One common technique used to examine the glands themselves is to evert the eyelid and to place a light source under the everted lid (on the outer surface of the lid) while examining the “transilluminated” image of the glands created by passing light through the lid. The image may be observed by an unaided eye, through a biomicroscope, or with a camera. Healthy glands appear as long, relatively straight forms, while dysfunctional glands may appear tortuous and swollen, and atrophied glands show a lack of continuity between the gland mass and the duct or orifice. In certain cases, infrared light is projected onto or through the everted lid, and an IR-sensitive camera is used to view the meibomian glands. The disadvantage of these transillumination techniques is that they require the lid to be everted, which is uncomfortable for most patients, and which can be difficult for the clinician to perform on some eyelids.
Another common technique for diagnosing MGD is to apply pressure to the eyelid while observing the meibomian gland ducts or orifices along the lid margin, usually with a magnifying means such as a biomicroscope. Healthy glands produce a clear oily secretion in response to the applied pressure. Glands that are partially dysfunctional produce less oil and/or cloudy oil. Glands that are more severely dysfunctional (inspissated) produce a paste-like secretion, which can only be squeezed out when more significant pressure is applied to the lid. Glands that are completely atrophied or that have had their orifices occluded do not produce any oil, even under high pressure.
MGD and blepharitis are chronic conditions with limited effective treatment. One of the most commonly recommended treatments is the application of a hot compress and massage (using the compress or fingertips) to the eyelid region. The intended goal of hot compress treatment is to heat up inspissated meibomian glands where thickened meibum resides, causing the meibum to soften and thereby more easily be expressed through the ducts. This process is thought to unclog the ducts and thereby allow the ducts to resume normal secretions and maintain a healthier tear film. Patients are generally instructed to apply a hot washcloth or other hot compress to the eyelid for five to ten minutes, multiple times daily. However, the efficacy of such an approach may be limited.
In-office treatment of MGD is often limited to squeezing the affected eyelids in order to express meibum from clogged or inspissated glands. Most clinicians use their fingertip or a cotton swab to apply pressure to the outer lid surface, but sometimes they also use a swab or a flat metal device (sometimes called a Mastrota paddle) on the inner lid while pushing against the outer lid in order to squeeze meibum out. All of these techniques are cumbersome for clinicians and painful for most patients.
Another in-office treatment uses intense pulsed light (IPL) around the eyes and eyelids. Such treatments are said to produce an improvement in dry eye symptoms over multiple sessions, but the mechanism is not understood and the equipment is expensive.
Still another in-office treatment is the TearScience LipiFlow® system, wherein heating elements are placed underneath the eyelids and an automated external controller maintains the heating elements at a target temperature while applying a pre-determined pattern of compression against the outer lids by way of inflatable bladders. This system is expensive and does not allow the clinician to control the treatment such to visually monitor the eyelid margin and meibomian gland ducts and to vary the level of heating and compression during the procedure in a manner that optimizes the treatment outcome. Such clinician control over the treatment may be important and is not present in the TearScience system.
Patients may also use saline drops or artificial tears to reduce the discomfort associated with dry eye; however, this approach fails to treat the dysfunctional meibomian glands and underlying inflammation. Additionally or alternatively, antibiotics may be prescribed to reduce the bacterial load in and around the eyelid. Topical and oral antibiotics are available, including oral tetracycline derivatives, which reduce certain bacteria and provide a mild anti-inflammatory effect; however, the administration of antibiotics may cause side effects or adverse allergic reactions, and the approach is often insufficient to provide significant long-term relief of blepharitis and MGD. Corticosteroids may be prescribed to reduce the inflammation; however, prolonged use of such steroids increases the risk of detrimental cortical lens changes, intraocular pressure spikes, and infection due to immunosuppression.
A need therefore exists for improved methods and devices to diagnose and treat meibomian gland dysfunction and blepharitis.